Avocados and Frost in Europe (plus info on the cold-hardiest avocados and how to grow them)

Philip Heinemeyer wrote:I tried rooting avocado cuttings and it didn't work. Now i am trying to layer my avocado ...

I was also unsuccessful at rooting avocado cuttings, though I only attempted this on one occasion with softwood ones. I'm really interested, Philip, to see if you can achieve rooting,  by using the 'layering' technique - I hope you have better luck than me so fingers crossed!

Here is a link to my efforts at 'layering' in 2020, with a young 'Hass' tree: https://imgur.com/a/6VfidCk

If I was to try this propagation technique again, I would do it a bit differently. Instead of a longitudinal cleft-cut & matchstick on the part of the stem buried in compost (described in the link just given) , I would carefully remove  a complete 360 degree ring of  the softer outer tissue (phloem) all the way around the stem, using a fresh razor blade.  The  aim of 'ringing' the stem is to alter the shoot/root hormone balance and hopefully this would initiate root growth in the 'ringed' region.  

Instead of layering stems that grow out from the base of the plant, it might be worth layering branches higher up the plant. Instead of a pot containing soil, you'd use a plastic bag (filled with compost) wrapped around the stem - I have found this to work well with Ficus benjamina. I have seen a couple of Youtube videos where this was achieved with avocado.

Hi,

Thanks for this great post with important informations. I live in parisian region (France) and I grafted 2 Mexicola scions onto a Hass and a west Indian seedling (separately). Here is a link for Hass :  

I would like to know if this combination will withstand cold temperatures. Looking at this post I guess no because even mexicola cuttings/seedlings suffered a lot. Around my locality, it snows 2-5 days (maximum) per year which is not regular annually. For the moment, grafts are doing really well. The west Indian seedling is now around 2 years old which has a bark at the bottom. The Hass seedling is starting to get premier barks at the bottom. I can share latest photographs if you want. Last year one of my hass seedling tree (1.5 years old) survived the winter in a balcony greenhouse without any maintainence apart from regular watering and manual ventilation. I guess I might need to air layer grafted mexicola scions to increase their cold hardiness but I am curious how it does if it gets established after 3 years onto hass/west indian seedling.  These 2 seedlings survived in the greenhouse last year. To protect all these plants, I might bring inside my apartment because I moved out onto a new one and my greenhouse won't fit on the new long and narrow balcony.

Thanks a lot for you help !

Happy gardening.

Hi Priyanshu, Welcome to Permies. I enjoyed your video (I like them short!).
It's always interesting to push the boundaries of a plants natural zones. Maybe you will get some heat island effect being in Paris? Good luck.

Priyanshu Uniyal wrote:Hi,
I grafted 2 Mexicola scions onto a Hass and a west Indian seedling (separately). I would like to know if this combination will withstand cold temperatures.

Hello Priyanshu,

I also really enjoyed your video, which was very nicely presented.  

The rootstock is normally the part of the graft combination that confers a degree hardiness to the plant as a whole, e.g. hardiness to freezing temperatures or resistance to root rot (the latter arising from cold wet or poorly-drained winter soils), as well as hardiness to other environmental stresses.  Therefore, for cold hardiness, the Mexican varieties are often used as the rootstock, grafted onto less hardy scions.  Therefore, I suspect your graft combination may have difficulty surviving the winter if the weather is significantly cold, i.e. below − 3 °C for long periods.

However, I can see the likely reason you've done the graft the other way round, i.e. hardy Mexicola scion grafted onto the less hardy rootstock. I am guessing you bought the leafy Mexicola shoots from someone, and the rootstock you used had to be grown from shop-bought fruits. The only way around this would be to try and root your Mexicola shoots, to make your own Mexicola rootstocks and, when these were established, graft the Hass or other varieties onto these as scions. However, to date, I haven't had much luck in rooting avocado cuttings, so am unable to advise you on this.

 

Nancy Reading wrote:Hi Priyanshu, Welcome to Permies. I enjoyed your video (I like them short!).
It's always interesting to push the boundaries of a plants natural zones. Maybe you will get some heat island effect being in Paris? Good luck.

Hi,

Thanks, I am glad you liked the video. Yeah, I really need some chaleur in this region for my plants. Keeping fingers crossed !

Happy gardening !

Priyanshu

Mike Guye wrote:

Priyanshu Uniyal wrote:Hi,
I grafted 2 Mexicola scions onto a Hass and a west Indian seedling (separately). I would like to know if this combination will withstand cold temperatures.

Hello Priyanshu,

I also really enjoyed your video, which was very nicely presented.  

The rootstock is normally the part of the graft combination that confers a degree hardiness to the plant as a whole, e.g. hardiness to freezing temperatures or resistance to root rot (the latter arising from cold wet or poorly-drained winter soils), as well as hardiness to other environmental stresses.  Therefore, for cold hardiness, the Mexican varieties are often used as the rootstock, grafted onto less hardy scions.  Therefore, I suspect your graft combination may have difficulty surviving the winter if the weather is significantly cold, i.e. below − 3 °C for long periods.

However, I can see the likely reason you've done the graft the other way round, i.e. hardy Mexicola scion grafted onto the less hardy rootstock. I am guessing you bought the leafy Mexicola shoots from someone, and the rootstock you used had to be grown from shop-bought fruits. The only way around this would be to try and root your Mexicola shoots, to make your own Mexicola rootstocks and, when these were established, graft the Hass or other varieties onto these as scions. However, to date, I haven't had much luck in rooting avocado cuttings, so am unable to advise you on this.

 

Hi Mike,

Thanks for your message. I might bring my grafted plants inside during winters when the temperature would drop around 5-7 °C. I will definitely try air layering. You think we can do this in softwoods (summer branch) or semi-softwoods as well ? During winters inside apartment is it feasible or should I only consider spring time as the best option? Cutting technique for me has always been very unpredictable for fruit plants except grapes. Do you think that to speed up the process, I might need to regraft the mexicola scion once it develops roots after air layering ? I have heard that avocado airlayering is difficult to get.

Priyanshu

Priyanshu Uniyal wrote:
I might bring my grafted plants inside during winters when the temperature would drop around 5-7 °C.

My limited experience, with growing avocado outdoors, is that any day or night temperatures above  0 °C are fine. There may even be some periods of limited growth during milder winter weather, i.e. when temperatures exceed around 10 °C.  Therefore, at the 5 to 7 °C that you mention, there is really no need to bring them indoors. In fact, if you bring them indoors, you may experience weak spindly growth during winter, without supplementing lighting provided by a horticultural lamp, as a result of a combination of warm room temperatures and low light quality/intensity.  If you leave them outdoors, just make sure they are sheltered from strong winds.

I will definitely try air layering. You think we can do this in softwoods (summer branch) or semi-softwoods as well? During winters inside apartment is it feasible or should I only consider spring time as the best option?

As you saw from the link I gave in a previous post, I was unsuccessful at air-layering avocado, so I am therefore unable to advise with any real confidence in this area. However, considering the best time to take cuttings (or do air-layering), I would guess that Spring would be the best time, just before or around the time of bud-break, when the sap is beginning to flow again.  

Cutting technique for me has always been very unpredictable for fruit plants except grapes. Do you think that to speed up the process, I might need to regraft the mexicola scion once it develops roots after air layering ? I have heard that avocado airlayering is difficult to get.

I'm not sure I understand clearly what you are saying here. However, if you can successfully air-layer the Mexicola scion, i.e. it grows roots, I would then grow it on its own roots and not bother with any further grafting onto West Indian or Guatemalan rootstocks - I don't see any advantage conferred on Mexicola by grafting onto these rootstocks.

This article by the RHS, on the principles of air layering for plants in general,  might be of interest: https://www.rhs.org.uk/propagation/air-layering-plants

Mike Guye wrote:
My limited experience, with growing avocado outdoors, is that any day or night temperatures above  0 °C are fine. There may even be some periods of limited growth during milder winter weather, i.e. when temperatures exceed around 10 °C.  Therefore, at the 5 to 7 °C that you mention, there is really no need to bring them indoors. In fact, if you bring them indoors, you may experience weak spindly growth during winter, without supplementing lighting provided by a horticultural lamp, as a result of a combination of warm room temperatures and low light quality/intensity.  If you leave them outdoors, just make sure they are sheltered from strong winds.

I have 2 very big windows (like patio windows) in my living room facing south east with balcony outside. So, in terms of sun exposure they are fine (If there is sun..). But often it gets very windy and wet in winters.

As you saw from the link I gave in a previous post, I was unsuccessful at air-layering avocado, so I am therefore unable to advise with any real confidence in this area. However, considering the best time to take cuttings (or do air-layering), I would guess that Spring would be the best time, just before or around the time of bud-break, when the sap is beginning to flow again.

Thanks 👍

I'm not sure I understand clearly what you are saying here. However, if you can successfully air-layer the Mexicola scion, i.e. it grows roots, I would then grow it on its own roots and not bother with any further grafting onto West Indian or Guatemalan rootstocks - I don't see any advantage conferred on Mexicola by grafting onto these rootstocks.

Sorry, what I meant by regrafting onto succesful mexicola air layering after rooting was to know if it would accelerate fruiting.

Priyanshu Uniyal wrote: I have 2 very big windows (like patio windows) in my living room facing south east with balcony outside. So, in terms of sun exposure they are fine (If there is sun..). But often it gets very windy and wet in winters.

Even with two very big windows, the light intensity will be significantly less than in Spring & Summer, and there will be less than 12 hours of daylight during the winter months (only 8-9 hours in December). Under such light conditions, you need to have cool temperatures to reduce or stop any growth during this period.  As I said before, if you encourage growth during the Winter months with warm room temperatures & poor light, you will get weak spindly growth.  

Sorry, what I meant by regrafting onto succesful mexicola air layering after rooting was to know if it would accelerate fruiting.

 
Fruiting in your Mexicola scions or cuttings will be precocious, only if  this material has been obtained from a mature tree, i.e. one that was already fruiting.  If they have been obtained from a fruiting tree, then you might get fruiting within 4-5 years, compared to say 8-20 years for material obtained from germinated seeds.  If you graft avocado scions obtained from germinated seeds, you will not accelerate their time to flowering/fruiting, and you may have to wait  8-20 years (or longer) until they flower/fruit.

 

Quick update on my young avocado plants :

It is close to 2-3 degrees here in Parisian region now and realfeel is -3 ! Regarding freezing point, should I take realfeel temperature into account to put inside my plants ? I am worried about my hass avocado grown from seedling (Image with 3 branches on a black container). It looks to be affected a lot by the cold so for the moment I have put it inside. I am wondering if I can reput it outside during daytime (realfeel close to 1-2) ?  I am still positive because there are some new buds (added images).

The other two grafted avocados are doing fine for the moment. One of them is Hass seedling onto mexicola scion (Video posted previously). I guess that brown tips are related to chloride and salt accumulation. I will do a test by boiling water and then put it onto plants with correct temperature. But wavy leaves are bothering me. I guess it is because of cold temperature because never saw it before. But could be different reasons.


Should I still let these grafted plants outside or should I bring them in ? I have a collective apartment floor heating system inside so not sure if it is good for plants to be in heating place at night and chilly weather outside. All photos were taken today.

Priyanshu Uniyal wrote: I guess that brown tips are related to chloride and salt accumulation  ... but it could be different reasons.

1. Yes, salt accumulation could be a factor: to eliminate this possibility flush the pot with at least 3 x pot volumes of a diluted water-soluble fertilizer - don't just use water.
2. It could also be that the plants are stressed generally, e.g. growing in pots stresses avocado unless the pots are very large - avocado doesn't like root-restriction at all.
3. They like a humid environment: it means that the air may well be too dry for them in winter in a heated room - perhaps spray the leaves daily with some water.

The Hass plant you show (before grafting) looks very unhealthy: it has almost lost all its leaves, and those remaining look stressed, being curled at the leaf margins - this suggests a problem with temperature/light/humidity levels, or any combination of these.  Any stress suffered by the Hass roots, will be transmitted to the Mexicola scion grafted onto it, so it's unsurprising if the leaves of your Mexicola scion also get 'tipburn' or become unhealthy in other ways.  You should only use healthy plant material for grafting.  

Priyanshu Uniyal wrote: Should I still let these grafted plants outside or should I bring them in ? I have a collective apartment floor heating system inside so not sure if it is good for plants to be in heating place at night and chilly weather outside. All photos were taken today.

Day temperatures (with good illumination) need to be higher than night temperatures.  If the night temperatures are warmer than in the daytime,  plants (of any species) will eventually die - they'll  simply respire themselves to death, leaves dropping off one-by-one, until there are none left and there is no energy left in the plant to regenerate. As I've mentioned in a previous post, your avocado will not thrive indoors in a warm heated room, when natural light levels are limited - to mitigate this you could buy a horticultural LED lamp to provide supplementary light during the winter.  If you do this, make sure the plants get at least 12 hours of illumination a day, though 16 hours would be better.  

I hope this helps Priyanshu. I know it's difficult, as there are a lot of things to consider, but I think with experimentation and all the trial-and-error that goes with that, you'll find a way to grow these that works for you.

Thanks Mike ! I might buy covers for grafted plants and leave them out for the time being. Il will put them on during night when temperature drops. It is likely to snow here today. Didn't happen here since a long time in early december. Well, that's how nature takes back it's control. I guess realfeel will be ideal temperature to consider as it is the best evaluator which takes into account multiple things  (Wind/Humidity/Temp/Dryness etc...) ? My grafted plants are doing well beyond my expectations outside. I will surely air layer them in spring time to remove mexicola scion (in case it works). But, until then, I will try to keep them alive.

For Hass plant (non-grafted), I am positive because there are many new buds. I am not a big fan of grow lights as it is very energy consuming even if it is LED. Specially in these difficult times when we might get power cuts here in France... Maybe grow light with solar energy option will be interesting. But I don't have that much amount of space in my apartment. I will keep the hass seedling plant inside for the time being.

Priyanshu Uniyal wrote:Thanks Mike ! I might buy covers for grafted plants and leave them out for the time being. I will put them on during night when temperature drops. It is likely to snow here today. Didn't happen here since a long time in early december.

Ideally, you should keep the plants indoors, in an unheated room for their first winter, on a sunny south-facing window sill.  However, if you keep the plants outside, try to ensure the temperature under the protective-covers doesn't drop below 0°C; ideally you should be monitoring the temperature. Make sure the covers enclose not only the plants, but also the ground (soil) as well, as this is a source of stored heat (thermal mass). If you don't include the ground under the covers, the temperatures under the covers will reach air temperatures very quickly, i.e. you'll have hardly any cold protection at all.

Priyanshu Uniyal wrote: I guess real feel will be ideal temperature to consider as it is the best evaluator which takes into account multiple things  (Wind/Humidity/Temp/Dryness etc...) ?

I don't know how you assess or calculate this: I use the temperature on a thermometer as my guide.

Priyanshu Uniyal wrote: My grafted plants are doing well beyond my expectations outside. I will surely air layer them in spring time to remove mexicola scion (in case it works). But, until then, I will try to keep them alive.

Yes, I think getting through the first three winters is the most challenging part ...

Priyanshu Uniyal wrote: I am not a big fan of grow lights as it is very energy consuming even if it is LED. Specially in these difficult times when we might get power cuts here in France...

I have used a 20 Watt LED kit (16 hour light period on a timer) in a foil-lined box for growing plants indoors. It doesn't make that much difference to my energy bill. You can do the calculations to work out how expensive it will be to run, based on your unit-price for electricity. If you want, I can give you the Amazon link for the LED grow lamp I bought...

Priyanshu Uniyal wrote:] Maybe grow light with solar energy option will be interesting.

Too expensive - not worth the investment !

Thanks Mike ! Sure ill will check LED light myself via internet. Can I put aluminium foil layer on the stem to protect it from cold ? Specially the grafted area ?

Priyanshu

Priyanshu Uniyal wrote:  Can I put aluminium foil layer on the stem to protect it from cold ? Specially the grafted area ?

I don't think this will make any difference, as the plant doesn't represent any significant thermal mass, i.e. it will get cooled very quickly by the cold air around it.

Avocados! Anyone here have success? I love love love avocados. I toss pits every where in the hopeful delusion that the genetic roulette will eventually pay off. I did have one in a very sheltered treed flood abatement area. It made it 8 years and 10 foot tall. Unfortunately our winters are getting colder here ( PNW usa) and summers hotter. It succumbed to a lower teens (f) cold snap. It had sailed through dips just below 20f. Alas my hopes dashed. Still tossing pits!

I have been experimenting in Texas with avocadoes since 2013, in climate zones 8a and now 9a.
Absolute temperatures under 24F are a problem for any avocado tree, but rapid drops in temperature seem even more important than the absolute low. California does not get the sudden, hard drops in temperature that Texas gets, so cold-hardy avocadoes that will survive in California will die in Texas.
I have killed a Lot of avocado trees in the last few years, probably more than 30, of every kind that I could get. Not all of the kinds can be gotten any more, since the Texas freeze in February 2021. Opal, Wilma and Pryor are no more.
https://floridafruitgeek.com/cold-hardy-avocados/
No grafted tree has survived for me. The ones that looked promising died in a late, hard, windy March freeze this year. Some seedlings and a few rootstocks are growing. One seedling was not harmed by that freeze. I am hopeful for it. It is from a Wilma seed.
There is at least one avocado orchard in Sabinas Hidalgo , Mexico at altitude, where it gets cold, in the northern edge of where avocados originated. I am trying to get seeds from that orchard to grow. Whatever survives winter will get to move to the next phase of the contest.
Genetic diversity within avocados is really more vast than in most plants, because mom & dad trees actually carry genes from the extended family, which you can't see.  https://www.intechopen.com/chapters/47902
Junior could have traits you did not expect, highly unpredictable. You need to grow  lot of seeds, see what survives, and wait a long time to try a fruit.

Hi John,

Welcome to Permies.

Thanks for these posts - especially Bryant Redhawk's excellent info!!

I only wish to add one thing: if you grow an avocado tree out from a seed with the old toothpicks-water-windowsill method, know that you cannot plant it directly into the ground and have it live: you must wean it off the water by planting into a pot and letting it grow more soil-compatible roots, or it WILL die.  Trust me on this

One more thought on siting your tender trees: remember the children's book "The Secret Garden"?  Takes place on an old manorial property in the UK, in a garden surrounded by a high brick wall;  obviously creating a lovely warm microclimate with the heat-retaining and wind-sheltering bricks.  So think about siting at a brick or cinderblock building with a Southern exposure OR, consider building a bottle-wall standing sculpture, maybe a c-shape if you don't do an enclosure, facing South.  It will be beautiful and provide the heat sink and wind protection to keep the trees alive.

Another old French trick was to pant tender fruit trees ON a dense (brick, stone...) wall, training them to the wall with pegs or eyes and wires/string: espalier

I repotted my seed grown (probably) Hass last spring and apparently shocked it terribly. It had bark and was about 2 1/5-3 foot tall. It promptly wilted down and appeared dormant all summer in my boiling hot greenhouse. As soon as the weather cooled in the fall it woke up and started growing again. I wondered if anyone else has seen this response to repotting and I would love to know if a seed grown this way would ever bloom. I have another plant that’s about the same size but without being sure what strain either of them are, I doubt I could ever see fruit from them.

What a great thread on Avocados!  Living in Central Florida we have areas that do get down into freezing temps and have to know what and how to grow them.  The biggest expert of this (among several others here) is Oliver Moore in Gainesville.  Not sure if he's on this Group but here's a post he did recently about Avocadoes.  I have a few from him that have survived freezes so far.  He is even colder and has plenty.  Besides growing the cold hardy he also has a greenhouse and multiple ideas for protection.
If you talk to him--invite him here if he isn't already.  I may do the same!

https://www.facebook.com/oliver.moore.1614/posts/pfbid0ogPCYbqrE438a6G4ZBuynddqufjcG1yFp5GpgFVuiZzPaSZF8y3BdP7aGTbFZ9u9l

Betsy Carraway wrote:Thanks for these posts - especially Bryant Redhawk's excellent info!(

Where can I find Bryant Redhawk's info?

Nice this thread came up again. I reread my own post 6 years ago ... Of those two avocado 'trees' I mentioned there one is still alive and well! So I made a photo of it, to show you here. Btw most of the year this plant is indoors, in this 'plant corner' in the living room. If I think of it I put it outdoors during 'summer rain'. The aloe plants (like that one next to the avocado) go outdoors in summer.

Lexie Smith wrote:I repotted my seed grown (probably) Hass last spring and apparently shocked it terribly. It had bark and was about 2 1/5-3 foot tall. It promptly wilted down and appeared dormant all summer in my boiling hot greenhouse. As soon as the weather cooled in the fall it woke up and started growing again. I wondered if anyone else has seen this response to repotting and I would love to know if a seed grown this way would ever bloom. I have another plant that’s about the same size but without being sure what strain either of them are, I doubt I could ever see fruit from them.

I noticed that the avocado plant doesn't like changes. One of those changes can be repotting. It reacts by dropping leaves. That's the most important reason why my avocado plant stays in my living room ... I fear it will drop leaves if I put it out, even on a nice summer day.

Hi,
I just want to know what happend this year (december 2022) snow on 12 and 13 December ? The Avocado tree on the video in London is alive ? any dommage on ? If someone can share a video on Youtube it could be very good.

Thanks and have a good day!

Paul Houdet, South of France, Nîmes

Paul Houdet-Segond wrote:Hi,
I just want to know what happend this year (december 2022) snow on 12 and 13 December ? The Avocado tree on the video in London is alive ? any dommage on ? If someone can share a video on Youtube it could be very good.

Thanks and have a good day!

Paul Houdet, South of France, Nîmes

Its cold at the moment but I would assume its fine its -4C here in the countryside which is not unusual and due to the heat island effect it appears to only dipping below freezing there tomorrow night. Six years ago we had -7C here and I would assume it was colder in London then.

Lexie Smith wrote: I repotted my seed grown (probably) Hass last spring and apparently shocked it terribly.

I've found that avocado are very sensitive to root disturbance. This is why you observed the 'transplant-shock', following  repotting. A good example of this: after  transplanting a small 'Fuerte' (2-3 years old) from one part of my garden to another, in June this year, it sulked for 2-3 months and only started to grow again in September.  Furthermore, avocados dislike having their roots restricted, which is why they do poorly in pots over the long-term, unless you have a pot with a circumference that extends out to, or further than, the drip-line! If you can, it's always better to have them growing in the ground outdoors, where they have ample room to horizontally spread their shallow root system.

Lexie Smith wrote: It promptly wilted down and appeared dormant all summer in my boiling hot greenhouse.

Two factors interacting here. The transplant-shock means that roots are not functioning optimally, therefore water uptake is compromised, made worse by your "boiling-hot greenhouse" which will only added to the evapo-transpirative demand on the plant. This inevitably led to the wilting you observed. Following transplanting, you need to keep the plant cool (out of direct heat/sun), e.g. using netting or other form of shading, until the roots re-establish.

Lexie Smith wrote: As soon as the weather cooled in the fall it woke up and started growing again.

Cooler weather = less evapo-transpiration from the leaves, roots re-establish, leading to plant recovery, which is what you observed ...

I've just realized my 'Hass' avocado tree is visible from space (satellite view on Google Maps) ...

Referring to the screenshot below - click on the image to make it bigger. Now look within the blue rectangle (which is my allotment plot) and you'll see a red circle. Within that circle, to the left, you'll see a bushy 5-6 year old 'Hass' tree, that was captured on image by Google this year (2022). The following imgur link shows you the tree that this satellite image corresponds to: https://imgur.com/a/5gflnlU

I have six other avocado trees growing on the same allotment plot, but at present they are too small [young] to see.

To give you an idea of scale in the picture below, the rectangular blue plot measures 25 metres x 18 metres.

@ Lexie Smith
This photo from my allotment plot, illustrates a strategy to minimize the effects of transplant-shock during root re-establishment:
(edit: legend below - line 2 should read "...better drainage  for the root system")

leigh gates wrote:Avocados!  I did have one in a very sheltered treed flood abatement area. It made it 8 years and 10 foot tall.... It succumbed to a lower teens (f) cold snap. It had sailed through dips just below 20f....

That's really interesting Leigh - I'm a bit curious to know more ...
Can you recall roughly how thick the lower trunk on this 8-year-old tree was?
After the tree succumbed to the extremely cold weather, did it show any signs of regrowth from the base of the trunk?

One important note here: people have mentioned problems with layering, sprouting seeds, and other methods of propagation.  Temperature is crucial to sprouting from seed: if you do it in Winter use a germination mat set at 70 degrees F; if layering, make sure you are able to keep moisture in there, and that the temps are not too cold (do this in Spring).  Avocadoes are tropical and go dormant in cold temps; you want the root development to happen before the seed rots or the scion dries out, and so temps (and humidity) must be considered.

Mike Guye - the tree was half way up the side of a flood abatement area, so not down in the cold sink at the bottom. It was an older area so treed but not yet an occluded canopy. I use my hand as a measuring device. With my fingers wide spread it is 7 inches tip of pinkie finger to tip of thumb. Also, bend my forefinger tightly and from knuckle to knuckle it is 1 inch middle section. I couldn’t quite completely enclose the trunk with both hands, so 14 inches + circumference? The depression ran almost South/North so Western exposure, which protected from the local  wind swirl. None of this was planned, lol, I just tossed the pits around the perimeter. It must have been a just right microclimate. The tree had healthy leaves and was starting to branch but no sign of fruiting. Since it is illegal to, ahem, “access” the area behind the fence I was only in there once, when I noticed it had grown tall enough to see. I should wander by in the spring and see if it came back.

leigh gates wrote: ... so 14 inches + circumference?

That's a really nice size for an 8-year-old tree.  That's a diameter of approximately 4½ inches - I always find diameters easier to visualize than circumferences. Yes, next Spring (2023), it would be interesting to see if it had regrown, surviving that very cold weather you mentioned. Do let us know either way. Thanks Leigh.  

The first photo below shows the location of my avocado trees - I call it Avocado Row.  The left photo shows how it looked during the recent cold weather (7 to 17 December 2022), the right photo following the thaw on 18 December.  Avocado Row  consists of 7 trees growing on a ridge, which itself is on a steep (1:4) N-facing slope. There are six protected trees (5 x 'Bacon' [1-year-old] & 1 x 'Fuerte' [2-years-old]) and furthest away you can see the 5½-years-old unprotected 'Hass',  which can be seen on satellite view on Google Maps (scroll back 6 posts).

Cold wintry weather has come early this year to St Leonards-on-Sea. In general, this kind of weather doesn't arrive here till January. It's been unusually cold too, with a continuous ground cover of snow and ice for 10 days, with freezing air temperatures persisting into daylight hours. Normally, following sunrise, winter air temperatures in this locality are above 0°C. Unfortunately, I wont be able to analyze the temperature datalogger (it continuously monitors air-temperatures around the avocado trees) until May 2023, as it's too much hassle to take it down for analysis and set it up again. The coldest night officially forecast for the area was around −3/−4 °C (16 December), but on the N-facing bank/slope of Avocado Row, temperatures tend to be colder than the official forecast.

Some details about the winter-protection you see in the photos.  An 80cm-high netting is around the plants to protect from wintry coastal gales, the same type of netting that is sold to protect carrots from carrot-root fly.  The tops of the supporting bamboo canes are covered with old plastic bottles: these support three  horticultural fleece covers for each plant, the thickness of each cover being 60 gsm.  The covers were bought online from Harrods Horticultural (UK) and are the 1.2m x 1.2m size. They are weighed down at their edges with planks of wood/bricks, and an extra-large pair of women's nylon tights is used to secure the covers, to stop them billowing when its windy.  This approach appeared very effective in protecting plants against the 10 days of cold weather - the covers remained permanently on the plants during the 10-day cold period.  

A significant observation ...
Any frost damage incurred was extremely minor, being restricted to plants that showed a flush of regrowth, in response to our unseasonably mild Autumn. Plants that appeared completely unscathed by the cold weather, were ones that went dormant in August, and didn't show any further regrowth in the Autumn. The second photo below shows a 'Fuerte'  (left) and a 'Bacon' (right), unscathed by the 10 days of cold weather,  examples of plants that became dormant in August.  Shutting down growth is a classic survival strategy of plants, in reducing the impact of environmental stress.

Links to my ongoing avocado blogs have now been updated with new photos ...

‘Hass’ - found by chance growing on my allotment plot ...
https://imgur.com/a/5gflnlU

'Fuerte' - recovery following winter damage ...
https://imgur.com/a/0XuODou

'Bacon' - grown from Morrisons supermarket seed (fruit imported from Spain) ...
https://imgur.com/a/FmRvs7d

'Del Rio' - my life history from seed to an adult tree ...
https://imgur.com/a/dAbixIe

Yesterday (16/01/2023), I went to visit the large fruiting avocado tree in SE London, the one originally made famous by youtuber Joe's Tropicals. As you can see from one of the photos below it's still fruiting. However it has suffered some major damage, i.e. the loss of a large limb, presumably ripped off in a gale. Apart from that, it still looks very healthy.  The trunk of the near tree is roughly 30 cm diameter.  To give you some idea of scale, the wall with the metal railings on top of it, that you see as you look west, is around 2.4 metres high.  I think the original estimation of tree height at 25 to 30 feet (8-10 metres) is about right.

If an avocado tree can grow so big (and even fruit!) in London, then maybe it will grow here in the Netherlands too. The climate is about the same.
I have a new small avocado seedling now here, grown last year (it was meant as a gift for my son, but he returned it because he was unsure if he could keep it alive). The larger avocado will remain my houseplant, but with this second one I can experiment and plant it in the garden (probably next to the loquat)